Copper-coated stainless steel tube



May 12., 1970 5. J. IANNONE 3,511,283

COPPER-COATED STAINLESS STEEL TUBE Filed Aug. 26, 1966 INV ENT ORdfizzzel ffdfzfza/ae MAMA/Me W ATTORNEYS United States Patent '03,511,283 COPPER-COATED STAINLESS STEEL TUBE Samuel J. Iannone, 15 W.Willow St., Beacon, N.Y. 12508 Filed Aug. 26, 1966, Ser. No. 575,416Int. Cl. F161 9/14 US. Cl. 138-143 3 Claims ABSTRACT OF THE DISCLOSUREThe present invention relates to a new and novel copper-coated stainlesssteel tube and method of manufacture thereof; and more particularly tocomposite tubing for use as a substitute for copper tubing.

The present invention is especially adapted for use in applicationswhere copper tubing is ordinarily employed, as for example in theplumbing field wherein copper tubing is extensively used due to thefacility with which it can be connected with the fittings required inordinary plumbing practice.

The copper-coated stainless steel tube of the present invention affordsa number of important advantages over conventional copper tubing. Thetubing of the present invention is considerably less expensive thanordinary copper tubing and is of no greater over-all size. Additionally,the tubing of the present invention meets all standards required ofcopper tubing, and yet the invention tubing is considerably lighter thancomparable copper tubing.

The utilization of an inner layer of stainless steel is highlyadvantageous where the tubing is used as a conduit means for corrosiveliquids. For example, water which is high in chlorides or fluorides andwhich has a pH on the acid side will pinhole copper tubing whereas itwill not pinhole the tubing of the present invention having a stainlesssteel inner layer. Accordingly, the in vention tubing has a much greatercorrosion resistance than conventional copper tubing.

Stainless steel tubing itself has not been employed in applications suchas the plumbing field and the like due to the difiiculty of solderingstainless steel itself; however, it has been discovered that when thestainless steel is coated with copper the composite tubing can bereadily soldered and sweated into joints in the very same manner andwith the same flux solders as are today employed with usual coppertubing. Accordingly, the composite tubing of the present invention maybe employed by a plumber with no difficulty and and without making anyadjustments in the normal plumbing procedures. The composite tubing ofthe present invention can be used with the same sleeves, angles, valvehousings and other coupling members as full copper tubing, and thejoints made in the same way.

A novel method is also provided in the present invention formanufacturing the unique composite tubing as discussed hereinabove.

The provision of the composite tubing according to the present inventionis particularly significant when it is considered that the cost of fullcopper tubing is continuously rising, and that stainless steel tubing ofabout .020 inch in thickness has approximately the same burst strengthof full copper tubing of about .080 inch in thickice ness. In addition,stainless steel tubing is approximately 12 percent lighter than fullcopper tubing of the same thickness. The cost of the composite tubing ofthe present invention is less than one-half the cost of comparablecopper tubing, thereby resulting in very substantial savings.

The completed composite tubing of the present invention includes theinnermost corrosion resistant layer of stainless steel having anintermediate layer of nickel electrolytically deposited thereon. Thisintermediate layer of nickel provides better adhesion with the outermostcopper layer, thereby providing a superior finished product.Additionally, during the method of manufacture of the tubing, the layerof nickel plating passivates the stainless steel tubes so as to reduceoxidation thereof until the final copper plating step of the process.

An object of the present invention is to provide new and novel compositetubing which can be used as a substitute in many applications for fullcopper tubing, and in particular which can be used in the plumbing fieldwith the same fittings and mounted in the same manner as full coppertubing.

Another object of the invention is to provide composite tubing whichmeets all the standards for full copper tubing, and yet which isconsiderably lighter for comparable applications.

Still another object of the invention is to provide composite tubingwhich can be substituted for full copper tubing and which isconsiderably less expensive and of no greater size.

A further object of the invention is the provision of composite tubinghaving greater corrosion resistance than comparable copper tubing.

A still further object of the invention is to provide a novel method ofmanufacturing composite tubing according to the present invention.

Other objects and many attendant advantages of the invention will becomemore apparent when considered in connection with the specification andaccompanying drawings, wherein:

FIG. 1 is a longitudinal section through apparatus employed for carryingout an electrolytic depositing step of the present invention;

FIG. 2 is a top perspective view partly broken away illustrating thecompleted composite tubing according to the present invention; and

FIG. 3 is a sectional view taken substantially along line 33 of FIG. 2looking in the direction of the arrows.

Referring now to the drawings wherein like reference charactersdesignate corresponding parts throughout the several views, FIG. 1illustrates apparatus employed in the present invention forelectrolytically depositing nickel and copper on a stainless steel tube.A tank 10 is provided which contains a suitable solution 12 therewithinas described hereinafter. A pair of support members 14 and 16 areillustrated as mounted upon the sides of the tank, and these supportmembers have bracket members 18 and 20 supported thereby. It will beunderstood that any suitable bracket or rack arrangement may be providedfor supporting a desired number of tubes in the tank at any one time, asingle tube being shown for the purpose of illustration.

These brackets 18 and 20 may be provided with suitable cutouts forsupporting an elongated metallic rod 22 which is formed of iron orsuitable electrically conductive material. The opposite ends 24 and 26of rod 22 are threaded. One end of the rod is provided with a threadedpost 30 of reduced dimension having a nut 32 disposed thereon forclamping a contact 34 against the end of the rod, contact 34 beingconnected with a lead 36 to a suitable source of electrical energy.

A pair of stepped end plugs 40 and 42 are provided with central boreshaving threads formed therewithin whereby the end plugs are threaded onthe opposite threaded ends of rod 22. These plugs 40 and 42 are adaptedto fit Within a stainless steel tube 46 as illustrated. It will be notedas seen in FIG. 1 that the tube 46 is supported by the plugs 40 and 42which have a fluid-tight seal therewith so that the solution within thetank cannot enter the interior of the tube.

Rod 22 is also provided with a plurality of radially outwardly extendingmembers 50 which may be flexible metallic wires of electricallyconductive material and which are arranged so as to define asubstantially helical path about the rod 22. These members 50 aresimilar to the bristles provided on a conventional bottle washer. Theouter ends of members 50 define a portion of a cylindrical surface ofsuch a dimension that the outer ends of members 50 are adapted to engagethe inner surface of tube 46 supported by the plugs 40 and 42.Accordingly, members 50 provide a substantially continuous electricalcontact throughout the length of the inner surface of the stainlesssteel tube 46, members 50 also, of course, assisting in supporting thetube in operative position as illustrated.

It is apparent that when electrical energy is impressed upon lead 36,the electrical potential will travel along rod 22 and through theelectrically conductive members 50 to the inner surface of tube 46 tothereby impress such potential upon member 46 throughout substantiallythe entire length thereof, thereby providing a very effective electricalconnection with the tube.

In carrying out the method of the present invention, tube '46 is firstmounted upon a rod 22 having end plugs 40 and 42 disposed thereon in theoperative relationship shown in FIG. 1. The assembly of rod 22, endplugs 40, 42 and tube 46 is then immersed in a suitable cleaning bathwhich comprises a strong non-etch alkali bath for removing oils andsoils therefrom. A typical cleaning solution may comprise Enbond S-61,manufactured by Enthone, Inc., of West Haven, Conn.

After the stainless steel tube has been cleaned with a suitable cleaningsolution, it is removed from such bath and rinsed with fresh water.

The stainless steel tubing is then immersed in a nickel bath wherein thearrangement asshown in FIG. 1 is employed. The solution in the nickelbath may contain about 240 grams per liter of nickel chloride and about36 grams per liter of hydrochloric acid. The tube is first made theanode of an electric circuit within the solution having nickelelectrodes as cathodes in the usual manner. A current of about 120'amperes per square foot is then passed through the solution for abouttwo minutes at a temperature of about 70 F. The tube is then made thecathode and the nickel electrodes the anodes in the circuit, and acurrent is passed through the circuit at a current density of about 120amperes per square foot for about two minutes until the desired layer ofnickel is electrolytically deposited on the outer surface only of thestainless steel tube 46.

The tube is then removed from the nickel bath and rinsed with freshwater.

The tube is then immersed in a suitable copper bath. This copper bathmay be either a cyanide or acid bath, or the two baths may be providedin sequence, that is, the tube may first be immersed in a cyanide copperbath and then in an acid copper bath.

An arrangement as shown in FIG. 1 is also employed in the copper bath.The solution of the cyanide copper bath may comprise about 27.5 gramsper liter of cuprous cyanide, about 35.4 grams per liter of sodiumcyanide, about 31.5 grams per liter of sodium carbonate, and about 31.5grams per liter of Rochelle salt. A layer of copper is thenelectroplated on the nickel previously deposited on the stainless steeltube at a current density of about 50 amperes per square foot, while thesolution is held at a temperature of about 120 F. until a suitable layerof copper is provided. The desired copper layer lies within a range ofapproximately 0.1 to 0.8 mil in thickness with an optimum thickness ofapproximately 0.2 mil.

If an acid copper bath is to be employed, the solution may contain about200 grams per liter of copper sulfate and about grams per liter ofsulfuric acid, and the electroplating may also be carried out at acurrent density of about 50 amperes per square foot until the desiredcoating of copper is obtained.

Referring now to FIGS. 2 and 3 of the drawings, the finished compositetubing is illustrated including an innermost continuous layer ofstainless steel 46 defining a bore 58 therewithin which serves toconduct liquid therethrough when in use. An intermediate continuouslayer 60 of nickel is electrolytically deposited on the outer surface ofthe tube 46, and an outermost continuous layer 62 of copper iselectrolytically deposited on the intermediate layer of nickel 60.

It is apparent from the foregoing that there is provided according tothe present invention a new and novel copper-coated stainless steel tubewherein the composite tubing may be used as a substitute in manyapplications for full copper tubing and in particular may be used in theplumbing field with the same fittings and additionally may be mounted inthe same manner as full copper tubing. The composite tubing of thepresent invention meets all standards required for full copper tubingand is at the same time considerably lighter. The tubing of the presentinvention is very economical in that its cost is substantially less thanthat of full copper tubing, and yet at the same time it is of no greatersize. The completed tubing of the present invention provides greatercorrosion resistance. A novel method is also provided for manufacturingthe composite tube of the present invention, this method ensuring thatthe stainless steel tubing will be properly coated, and only on theouter surface thereof, while the inner surface of the stainless steeltube remains in its original condition.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive.

What is claimed is:

1. Composite tubing for use as a substitute for copper tubing and whichcan be used with the same fittings and mounted in the same manner ascopper tubing comprising a tube open at the opposite ends thereof andincluding an innermost layer of stainless steel which defines a boretherewithin, an outer intermediate layer of nickel supported on saidlayer of stainless steel, and an outermost layer of copper supported onsaid layer of nickel.

2. Composite tubing as defined in claim 1, wherein each of said layersis continuous in a peripheral direction on the outer surface only andextends throughout the length of said tube.

3. Composite tubing as defined in claim 2, wherein said intermediatelayer of nickel is electrolytically deposited on said innermost layer ofstainless steel, and said outer layer of copper is electrolyticallydeposited on said intermediate layer of nickel.

References Cited UNITED STATES PATENTS 645,187 3/1900 Richmondt l38--1461,778,818 10/1930 Thorman 138-146 1,930,191 10/1933 Bundy 138-1452,311,138 2/ 1943 Swartz 138-143 XR H. HAMPTON HUNTER, Primary ExaminerUS. Cl. X.R. 138l46

